Cylinder with yieldable periphery

ABSTRACT

A rotary machine having a cylinder which runs in pressure relationship with a cooperating cylinder. At least one of the cylinders has an axially extending discontinuity in the periphery which periodically causes an interruption in the pressure between the cylinders with the discontinuity having a yieldable portion adjacent the discontinuity for effecting a more gradual pressure change. The yieldable portion is formed by undercutting the cylinder periphery with a recess to provide a cantilevered yieldable lip against the discontinuity. The recess is filled with shims to control the yieldability of the lip.

I Umted States Patent 1 1 3,589,285

[72] Invento R 1- An r 2,793,588 5/1957 Stempel lOl/4l5.l Brecksville,0hl0 2,898,854 8/1959 Crawford lOl/4lS.l 21 AppLNo. 6.333 3,156,l84 11/1964 Shank 101/4151 [22] Filed Jan. 20,1970 3,l07,6l0 10/1963 Strahorn 101/4151 [45] Patented June 2 ,1 3,237,557 3/1966 Worthington et al.. 101/378 [73] Assignee Hnrrl -lnle yp rp r n 3,244,098 4/1966 Bryer 101/375 Cleveland. Ohio Continuation of application Ser. No. pmrmry 686,049, Now-'28, 1967, now abandoned. Reed Atl0rney--Yount, Flynn & Tarolli {54] CYLINDER WITH YIELDABLE PERIPHERY 6 Claims 4 Drawing Flgs' ABSTRACT: A rotary machine having a cylinder which runs U.S. in re sure relationship with a cooperating cylindef At least 101/376 one of the cylinders has an axially extending discontinuity in [5 1] Int. Cl B4" 13/08 the periphery which periodicany causes an interruption i h [50] Field of Search 101/212, pressure between the cylinders with the discontinuity h i a 213-216,?11376-3Z8-379,382v412,415-1: yieldable portion adjacent the discontinuity for effecting a I 271/ 30"82 more gradual pressure change. The yieldable portion is formedb undercuttin thec linder eri her witharecess to [56] References Cited provide a cantilevered yielda lile lip :gai nst tl te discontinuity.

UNITED STATES PATENTS The recess is filled with shims to control the yieldabiiity of the 2,378,523 6/1945 Worthington 101/409 lip.

PATENTEDJUHZSISYI 3,589,285

29 I as fl 54a M m 1 29 W'k HQ .4

INVENTOR.

ROBERT J ANDERSON ATTORNE YS CYLINDER WITH-ll YIELDABLE PERIPHERY This is a continuation application of copending application Ser. No. 686,049, filed Nov. 28, 1967, now abandoned.

An object of the present invention is to provide a new and improved printing press or other rotary machine in which a blanket cylinder or other cylinder having a discontinuity therein runs in pressure relationship with a cooperating member and is constructed so that the spring rate of the periphery of the cylinder adjacent the discontinuity can be controlled in an effective, simple and novel manner to control the forces which occur as the discontinuity passes the line of engagement between the cylinder and member.

A further object of the present invention is to provide a new and improved cylinder construction for a printing press blanket cylinder or similar cylinder which runs in pressure relationship with a cooperating member with the construction being such that the spring rate of a portion of the periphery of the cylinder adjacent a cylinder gap may be readily controlled to minimize print disturbance caused by the forces which are created or released as the gap passes the cooperating member.

Further objects and advantages of the present invention will be apparent from the following detailed description thereof made with respect to the accompanying drawings forming a part of the present specification for all matter disclosed therein and in which:

FIG. 1 is an illustrative view of cylinders of a sheet fed lithographic printing press embodying the present invention;

FIG. 2 is a fragmentary sectional view of the blanket cylinder of the press of FIG. ll;

FIG. 3 is an enlarged fragmentary view of the structure shown in FIG. 2; and

FIG. 4 is a fragmentary plan view of one blanket cylinder.

While the present invention is susceptible of use in various rotary machines utilizing a cylinder with a discontinuity in the surface thereof which causes the pressure between the cylinder and a cooperating member to be momentarily interrupted as the discontinuity passes the line of engagement therebetween, the present invention is particularly useful in a lithographic sheet fed printing press where gaps in cylinders for clamps, reels or grippers cause a momentary interruption of pressure between cooperating cylinders and print disturbances which render the printed product of poor or unacceptable quality. Such cylinders are normally gear driven with the gears of cooperating cylinders being in mesh. It is desirable that all forces which are capable of adversely affecting this gear mesh be controlled so as not to adversely affect the resultant print. One such force is the normal tendency of cylinders to bounce due to the intermittent pressure changes resulting from the discontinuity in the cylinders periphery.

Referring to the drawing, FIG. ll shows the printing cylinders of a lithographic printing press. The printing cylinders include a blanket cylinder I which runs in pressure engagement with an impression cylinder 11. A conventional blanket 12 is held onto the periphery of the blanket cylinder by conventional blanket bars and reels which are disposed in an axially extending gap M in the periphery of the blanket cylinder 10.

The impression cylinder 11 has sheet grippers for gripping the leading edge of a sheet to be printed which are disposed in an axially extending gap 15 in the periphery thereof. The gaps M and 115 of the cylinders 10 and 11 register and pass each other at the print line as the cylinders are rotated. The blanket and impression cylinders operate with a pressure relationship when sheet material is passing therebetween. This pressure relationship between the cylinders is momentarily interrupted as the gaps pass each other. Heretofore, it has been found that this interruption and reestablishment of pressure as the cylinder gaps pass each other tends to affect the gear mesh between the cylinders and to cause bouncing between the cylinders resulting in print disturbances. To minimize the effect of the gaps passing and particularly the high forces which are created as pressure is reestablished, portions of the blanket cylinders adjacent the gap have been made with a lower spring rate than the remaining periphery of the cylinder so that the pressure change is more gradual and less abrupt. In the present invention, the yieldability of the periphery of the cylinder is controlled in a simple and effective manner.

Referring to FIG. 2, the blanket cylinder 10 comprises an annular member 20 forming the periphery of the cylinder. The annular member 20 terminates in leading and trailing end portions forming part of the sides of the gap 14 which extend inwardly of the cylinder at the leading and trailing ends respectively of the periphery of the blanket cylinder. The leading end portion 20a of the annular member 20 is notched to receive a blanket bar 23 having a bar 24 to which the leading end of the blanket is secured. The blanket bar is adjustable away from the leading end of the cylinder periphery by operation of screws 25 threaded into member 26 depending from the bar 23. The screws 25 are spaced along the length of member 26 and bear against pins 28 which are slidably received in the member 26 and project therefrom to bear against the end portion 20a of the annular member 20. The blanket bar may be moved to tighten the blanket onto the blanket cylinder by threading the screws 25 inwardly into the member 26 to force the pins 28 outwardly.

In the illustrated embodiment, the end portion 20a of annular member 20 is laminated to lower its spring rate. In the illustrated embodiment the end portion 20a has an elongated recess 30 extending inwardly from the gap 14 to underlie the peripheral portion of the cylinder adjacent the gap 14 and provide a cantilevered lip 31 adjacent the gap with the free end of the cantilevered lip 31 being at the gap and forming the leading edge of the cylinder periphery. As is shown in FIG. 3, the thickness of the lip 31 increases proceeding away from the gap so that the spring rate of the lip 31 gradually increases as one proceeds along the cylinder periphery away from the gap 14.

In the preferred embodiment, the recess 30 extends the full length of the leading edge of the cylinder periphery and is defined by opposed straight walls 3.2, 33 which extend inwardly from the end 20a of the annular member 20. At the ends of the cylinder, as shown in FIG. 4, bearers 29 are tightly bolted flush with the ends of the cylinder which run in pressure relationship with corresponding bearers on the cooperating cylinders. Between each bearer and the active periphery of the cylinder is a slight recess or gutter 34, which is provided for overhanging of dampener and inker form rolls in the case of a plate cylinder, and is conveniently used also on blanket and impression cylinders. At the ends of the lip 31 adjacent the side of each bearer, the lip is relieved a few thousandths of an inch as indicated at 34a, in order to permit yielding of the lip without friction at the ends.

In the illustrated embodiment, a metal bar 35 is disposed in the recess 30 to fill a major portion of the recess. The bar 35 engages the adjacent wall 33 of the recess 30, which is the wall thereof remote from the outer periphery of the cylinder, and is of a height less than that of the recess. Additional laminations in the form of metal shims 36 are disposed between the bar 35 and the side 32 of the recess 30 to essentially fill the recess.

In the illustrated embodiment, the bar 35 preferably extends at least the full length and depth of the recess 30 so as to abut the back of its receiving recess and to extend to the adjacent side of the gap. The shims 36 also preferably extend at least for the full length and depth of the recess 30 to fill the space between the bar 35 and the cantilevered lip 31. The stiffening effect of the laminations will depend upon the number of laminations and the air between adjacent laminations. If a lower spring rate is desired, a thinner bar than that shown in the drawing may be used for the bar 35 and additional shims inserted into the stack to fill the additional space between the bar and the cantilevered lip. This provides a larger stack of shims and increases the softness and compressibility of the shim stack so that the spring rate is reduced. Conversely, a thicker bar with a smaller shim stack will increase the spring rate and make the cantilevered lip 31 stiffer. In certain applications, the bar 35 may closely fit the recess 30 to entirely fill the latter and provide the laminated end portion. Such an end portion a will have a softer spring rate than a solid one piece end portion since there will be slight irregularities and unevenness in the surfaces of the bar and recess which will allow the lip 31 to give more as compared to a nonlaminated, solid end portion.

It will be understood that various combinations of bars and shim stacks may be used to readily acquire the desired stiffness for the cantilevered lip 31 which constitutes the outermost lamination of the end portions 200. The shims and bars may also be shorter than the axial length of active periphery of the cylinder. In such a case the laminations are preferably disposed in end-to-end relationship in each layer with the laminations in the layers preferably overlapping the adjacent ends of the laminations in the adjacent layers.

The bar 35 and the shims 36 extend to the outside of the gutters 34 and in the illustrated embodiment are held in place by screws located in oversized recesses in the gutters and which" pass through the bar and laminations and thread into the bottom of the gutters to clamp the ends of the bar laminations against the annular member 20.

If desired, jacking-out screws may be threaded into the bar 35 to facilitate its removal from the recess 35.

One of the advantages of the present invention is that the shims and bars may be readily inserted and removed. The shims are of thin metal and preferably extend the axial length of the periphery of the cylinder and also for substantially the full depth of the recess 30. inherently, such metal shims tend to be wavy and this waviness not only facilitates the cushioning effect but may also be used to hold the shims in place without additional securing means.

While the invention has been illustrated at the leading edge of the periphery of the blanket cylinder it), it will be understood that it may be duplicated at the trailing edge to minimize the forces created by the abrupt pressure change as the gaps on the cylinders 10, 11 come into registry. Moreover, it will be understood by those skilled in the art that the disclosed invention may be incorporated in various cylinders of different types of rotary machines where running pressure between the cylinder and another member is periodically interrupted by a discontinuity in the cylinder periphery.

it can now be seen that the present invention has provided a new and improved cylinder arrangement for a rotary machine which enables the spring rate of the'cylinder periphery adjacent a discontinuity in the periphery to be readily controlled. The arrangement is such that a laminated structure is provided whose spring rate depends upon the depth and extent of the laminations. In the illustrated embodiment, the shims provide the laminations and as the shim stack is increased or decreased, the spring rate is made softer or stiffer.

Having described my invention, 1 claim:

1. In a printing press, a pair of cooperating rotating cylinders operating in pressure relationship, at least one of said cylinders defining an outer surface for supporting a printing element dtiring a printing operation, said one of said cylinders having an axially extending gap in the periphery thereof which causes the pressure between the peripheries of the cylinders to change as the cylinders rotate, and means for absorbing shock and maintaining print pressure against the printing element adjacent to said gap during rotation of said cylinders, said means including a circumferentially cantilevered portion of said one cylinder which extends circumferentially from one edge portion of said gap for substantially the entire length of said cylinder and is resiliently deflectable and located radially inwardly of the printing element, said cantilevered portion being in pressure relationship with the other cylinder of said pair of cylinders during at least a portion of a cycle operation of said printing press and having an inner surface which cooperates with an inner surface of said one of said cylinders to at least partially define a longitudinal recess in said one cylinder adjacent to said gap, said inner surfaces of said cantilevered portion and one cylinder extending longitudinally for substantially the entire axial length of said one cylinder, and

lamination means for supporting said cantilevered portion, said lamination means being disposed in said recess radially inwardly of said cantilevered portion with an outer surface of said lamination means disposed in abutting engagement with said inner surface on said cantilevered portion throughout the entire length and width of said inner surface of said cantilevered portion and throughout the entire length and width of said outer surface of said lamination means and an inner surface of said lamination means disposed in abutting engagement with said inner surface of said one cylinder throughout the entire length and width of said inner surface of said one cylinder and throughout the entire length and width of said inner surface of said lamination means so that said lamination means fills the entirety of said recess between said inner surface of said cantilevered portion and said inner surface of said one cylinder, said lamination means being compressible between said cantilevered portion and said inner surface of said one cylinder throughout substantially the entire length of said one cylinder to absorb shock and dampen movement of said pair of cylinders produced in response to the change in pressure between the peripheries of said pair of cylinders.

2. In a printing press as defined in claim 1 wherein said lamination means includes a bar and a plurality of shims, said bar having a thickness which is at least twice as great as the thickness of one ofsaid shims.

3. In a printing press, a cylinder as defined in claim 1 wherein said lamination means and recess are substantially equal in axial extent and circumferential depth to said cantilevered portion.

4. In a printing press as set forth in claim 1 further including means disposed in said gap for securing the printing element to said one of said cylinders, said means for securing the printing element to said one of said cylinders including a pair of clamping surfaces circumferentially spaced from said lamination means for clampingly engaging said printing element independently of said lamination means. 1 a

5. In a printing press, a pair of cooperating rotating cylinders operating in pressurerelationship, at least one of said cylinders defining an outer surface for supporting a printing element during a printing operation, said one of said cylinders having an axially extending gap in the periphery thereof which causes the pressure between the peripheries of the cylinders to change as the cylinders rotate, and means for absorbing shock and maintaining print pressure against the printing element adjacent to said gap during rotation of said cylinders, said means including a circumferentially cantilevered part of said one cylinder, said cantilevered part being located radially inwardly of the printing element and being in pressure relationship with the other cylinder of said pair of cylinders during at least a portion of a cycle operation of said printing press, said cantilevered part of said one cylinder including a fixed end portion which is circumferentially spaced from said gap and a free end portion which extends circumferentially from said gap toward said fixed end portion, said free end portion of said cantilevered part being resiliently deflectable and having an inner surface which cooperates with an inner surface of said one of said cylinders to at least partially define a longitudinal recess in said one cylinder adjacent to said gap, and lamination means for supporting said cantilevered part, said lamination means filling said recess and being disposed radially inwardly of said free end portion of said cantilevered part with an outer surface of said lamination means disposed in abutting engagement with said inner surface on said free end portion of said cantilevered part and an inner surface of said lamination means disposed in abutting engagement with said inner surface of said one cylinder at a location radially inwardly of said free end portion of said cantilevered part, said lamination means being compressible between said free end portion of said cantilevered part and said inner surface of said one cylinder throughout substantially the entire length of said one cylinder to absorb shock and dampen movement of said pair of cylinders produced in response to the change in pressure between the peripheries of said pair of cylinders.

6. in a printing press, a pair of cooperating rotating cylinders operating in pressure relationship, at least one of said cylinders defining an outer surface for supporting a printing element during a printing operation said one of said cylinders having an axially extending gap in the periphery thereofwhich causes the pressure between the peripheries ofthe cylinders to change as the cylinders rotate, and means for absorbing shock and maintaining print pressure against the printing element adjacent to said gap during rotation of said cylinders, said means including a circumferentially cantilevered part of said one cylinder, said cantilevered part being located radially inwardly of the printing element and being in pressure relationship with the other cylinder of said pair of cylinders during at least a portion of a cycle operation of said printing press, said cantilevered part of said one cylinder including a fixed end portion which is circumferentially spaced from said gap and a free end portion which extends circumferentially from said gap toward said fixed end portion, said free end portion of said v cantilevered part being resiliently deflectable and having an inner surface which cooperates with an inner surface of said one of said cylinders to at least partially define a longitudinal recess in said one cylinder adjacent to said gap, and a metal bar extending longitudinally of said one cylinder and having a thickness which is the same as the radial thickness of said recess at a location radially inwardly of said free end portion of said cantilevered part, said bar being disposed in said recess with an outer surface of said bar in abutting engagement with said inner surface on said free end portion of said cantilevered part and an inner surface of said bar in abutting engagement with said inner surface of said one cylinder at a location radially inwardly of said free end portion of said cantilevered part, said cantilevered part being supported by said bar to absorb shock and dampen movement of said pair of cylinders produced in response to the change in pressure between the peripheries of said pair of cylinders. surface of said lamination means disposed in abutting engagement with said inner surface on said free end portion of said cantilevered part and an inner surface of said lamination means disposed in abutting engagement with said inner surface of said one cylinder at a location radially inwardly of said free end portion of saidcantilevered part, said lamination means being compressible between said free end portion of said cantilevered part and said inner surface of said one cylinder throughout substantiallythe entire length of said one cylinder to absorb shock and dampen movement of said pair of cylinders produced in response to the change in pressure between the peripheries of said pair of cylinders.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION ,5 9, 5 Dated June 9, 97

Patent No.

l e Robert J. Anderson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the claims:

Claim 6, 215mm 6, line 11, delete "surface of said 1aminat1on...said pair of cylinders."

Signed and sealed this 16th day of November 1 971 (SEAL) Atte st:

EDWARD M.FIETCHER,JR. ROBERT GO'ITSCHALK Acting Commissioner of Patents Attesting Officer USCOMM-DC 6O 37 6-909 FORM PO-\O5O (10-69) a u s sovsmmun Pnmvms orncz. nu o-au-ua 

1. In a printing press, a pair of cooperating rotating cylinders operating in pressure relationship, at least one of said cylinders defining an outer surface for supporting a printing element during a printing operation, said one of said cylinders having an axially extending gap in the periphery thereof which causes the pressure between the peripheries of the cylinders to change as the cylinders rotate, and means for absorbing shock and maintaining print pressure against the printing element adjacent to said gap during rotation of said cylinders, said means including a circumferentially cantilevered portion of said one cylinder which extends circumferentially from one edge portion of said gap for substantially the entire length of said cylinder and is resiliently deflectable and located radially inwardly of the printing element, said cantilevered portion being in pressure relationship with the other cylinder of said pair of cylinders during at least a portion of a cycle operation of said printing press and having an inner surface which cooperates with an inner surface of said one of said cylinders to at least partially define a longitudinal recess in said one cylinder adjacent to said gap, said inner surfaces of said cantilevered portion and one cylinder extending longitudinally for substantially the entire axial length of said one cylinder, and lamination means for supporting said cantilevered portion, said lamination means being disposed in said recess radially inwardly of said cantilevered portion with an outer surface of said lamination means disposed in abutting engagement with said inner surface on said cantilevered portion throughout the entire length and width of said inner surface of said cantilevered portion and throughout the entire length and width of said outer surface of said lamination means and an inner surface of said lamination means disposed in abutting engagement with said inner surface of said one cylinder throughout the entire length and width of said inner surface of said one cylinder and throughout the entire length and width of said inner surface of said lamination means so that said lamination means fills the entirety of said recess between said inner surface of said cantilevered portion and said inner surface of said one cylinder, said lamination means being compressible between said cantilevered portion and said inner surface of said one cylinder throughout substantially the entire length of said one cylinder to absorb shock and dampen movement of said pair of cylinders produced in response to the change in pressure between the peripheries of said pair of cylinders.
 2. In a printing press as defined in claim 1 wherein said lamination means includes a bar and a plurality of shims, said bar having a thickness which is at least twice as great as the thickness of one of said shims.
 3. In a printing press, a cylinder as defined in claim 1 wherein said lamination means and recess are substantially equal in axial extent and circumferential depth to said cantilevered portion.
 4. In a printing press as set forth in Claim 1 further including means disposed in said gap for securing the printing element to said one of said cylinders, said means for securing the printing element to said one of said cylinders including a pair of clamping surfaces circumferentially spaced from said lamination means for clampingly engaging said printing element independently of said lamination means.
 5. In a printing press, a pair of cooperating rotating cylinders operating in pressure relationship, at least one of said cylinders defining an outer surface for supporting a printing element during a printing operation, said one of said cylinders having an axially extending gap in the periphery thereof which causes the pressure between the peripheries of the cylinders to change as the cylinders rotate, and means for absorbing shock and maintaining print pressure against the printing element adjacent to said gap during rotation of said cylinders, said means including a circumferentially cantilevered part of said one cylinder, said cantilevered part being located radially inwardly of the printing element and being in pressure relationship with the other cylinder of said pair of cylinders during at least a portion of a cycle operation of said printing press, said cantilevered part of said one cylinder including a fixed end portion which is circumferentially spaced from said gap and a free end portion which extends circumferentially from said gap toward said fixed end portion, said free end portion of said cantilevered part being resiliently deflectable and having an inner surface which cooperates with an inner surface of said one of said cylinders to at least partially define a longitudinal recess in said one cylinder adjacent to said gap, and lamination means for supporting said cantilevered part, said lamination means filling said recess and being disposed radially inwardly of said free end portion of said cantilevered part with an outer surface of said lamination means disposed in abutting engagement with said inner surface on said free end portion of said cantilevered part and an inner surface of said lamination means disposed in abutting engagement with said inner surface of said one cylinder at a location radially inwardly of said free end portion of said cantilevered part, said lamination means being compressible between said free end portion of said cantilevered part and said inner surface of said one cylinder throughout substantially the entire length of said one cylinder to absorb shock and dampen movement of said pair of cylinders produced in response to the change in pressure between the peripheries of said pair of cylinders.
 6. In a printing press, a pair of cooperating rotating cylinders operating in pressure relationship, at least one of said cylinders defining an outer surface for supporting a printing element during a printing operation, said one of said cylinders having an axially extending gap in the periphery thereof which causes the pressure between the peripheries of the cylinders to change as the cylinders rotate, and means for absorbing shock and maintaining print pressure against the printing element adjacent to said gap during rotation of said cylinders, said means including a circumferentially cantilevered part of said one cylinder, said cantilevered part being located radially inwardly of the printing element and being in pressure relationship with the other cylinder of said pair of cylinders during at least a portion of a cycle operation of said printing press, said cantilevered part of said one cylinder including a fixed end portion which is circumferentially spaced from said gap and a free end portion which extends circumferentially from said gap toward said fixed end portion, said free end portion of said cantilevered part being resiliently deflectable and having an inner surface which cooperates with an inner surface of said one of said cylinders to at least partially define a longitudinal recess in said one cylinder adjacent to said gap, and a metal bar extending longitudinally of said one cylinder and having a thickness which is the same as the radial thickness of said recess at a location radially inwardly of said free end portion of said cantilevered part, said bar being disposed in said recess with an outer surface of said bar in abutting engagement with said inner surface on said free end portion of said cantilevered part and an inner surface of said bar in abutting engagement with said inner surface of said one cylinder at a location radially inwardly of said free end portion of said cantilevered part, said cantilevered part being supported by said bar to absorb shock and dampen movement of said pair of cylinders produced in response to the change in pressure between the peripheries of said pair of cylinders.
 6. In a printing press, a pair of cooperating rotating cylinders operating in pressure relationship, at least one of said cylinders defining an outer surface for supporting a printing element during a printing operation, said one of said cylinders having an axially extending gap in the periphery thereof which causes the pressure between the peripheries of the cylinders to change as the cylinders rotate, and means for absorbing shock and maintaining print pressure against the printing element adjacent to said gap during rotation of said cylinders, said means including a circumferentially cantilevered part of said one cylinder, said cantilevered part being located radially inwardly of the printing element and being in pressure relationship with the other cylinder of said pair of cylinders during at least a portion of a cycle operation of said printing press, said cantilevered part of said one cylinder including a fixed end portion which is circumferentially spaced from said gap and a free end portion which extends circumferentially from said gap toward said fixed end portion, said free end portion of said cantilevered part being resiliently deflectable and having an inner surface which cooperates with an inner surface of said one of said cylinders to at least partially define a longitudinal recess in said one cylinder adjacent to said gap, and a metal bar extending longitudinally of sAid one cylinder and having a thickness which is the same as the radial thickness of said recess at a location radially inwardly of said free end portion of said cantilevered part, said bar being disposed in said recess with an outer surface of said bar in abutting engagement with said inner surface on said free end portion of said cantilevered part and an inner surface of said bar in abutting engagement with said inner surface of said one cylinder at a location radially inwardly of said free end portion of said cantilevered part, said cantilevered part being supported by said bar to absorb shock and dampen movement of said pair of cylinders produced in response to the change in pressure between the peripheries of said pair of cylinders. surface of said lamination means disposed in abutting engagement with said inner surface on said free end portion of said cantilevered part and an inner surface of said lamination means disposed in abutting engagement with said inner surface of said one cylinder at a location radially inwardly of said free end portion of said cantilevered part, said lamination means being compressible between said free end portion of said cantilevered part and said inner surface of said one cylinder throughout substantially the entire length of said one cylinder to absorb shock and dampen movement of said pair of cylinders produced in response to the change in pressure between the peripheries of said pair of cylinders. 